This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-242845, filed Aug. 10, 2000, the entire contents of which are incorporated herein by reference.
1. Field of the Invention
The present invention relates to a natator in a water tank such as an artificial fish which swims in a water tank of, for example, an aquarium, a controlling apparatus and a position measuring apparatus of this natator in a water tank.
2. Description of the Related Art
In recent years, as a natator in a water tank, there has been considered an artificial fish which is caused to swim in a water tank of, for example, an aquarium. The artificial fish includes therein a battery, a motor, and a control portion and the like for driving and controlling this motor, and is caused to swim in a water tank by moving a fin and others by the motor in accordance with a control command. The control of realistic movements of the artificial fish in water or three-dimensional position measurement in water for guiding the built-in battery to a non-contact charging mechanism portion is essential.
Although there has conventionally been a liquid level meter (two-dimensional) in a tank which utilizes supersonic waves to measure a propagation time thereof and further measure a liquid level or a liquid current meter for measuring a speed of a liquid flowing in a pipe, the position measuring apparatus for measuring a three-dimensional position of a natator in a water tank is not yet to come into practical use.
It is an object of the present invention to provide a natator in a water tank whose three-dimensional position can be measured, a control apparatus thereof, and a position measurement apparatus for measuring a three-dimensional position of the natator in a water tank.
The above-described aim can be achieved by the following invention.
That is, according to one aspect of the present invention, a natator in a water tank is comprised of: a radio wave receiver for receiving a signal by radio waves transmitted from the outside; an ultrasonic transmitter for transmitting ultrasonic waves based on the signal received by the radio wave receiver; and a natatory operation servo motor which is controlled and driven based on the signal received by the radio wave receiver.
Consequently, the natator in a water tank is driven and controlled in accordance with the signal transmitted from the outside and can transmit to the outside information concerning its own position by transmitting ultrasonic waves. Further, by providing a battery, power required for the radio wave receiver, the ultrasonic transmitter and the natatory operation servo motor is supplied.
According to a second aspect of the present invention, a control apparatus of a natator in a water tank is comprised of: a radio wave transmitter for transmitting a control command by radio waves to a natator in a water tank; a radio wave receiver which is provided in the water tank and receives radio waves transmitted from the radio wave transmitter; and a natatory operation servo motor which is driven and controlled in accordance with a control command received by the radio wave receiver.
As a result, the control apparatus of a natator in a water tank can transmit a control signal to the natator in a water tank from the outside and control drive of the natator in a water tank based on this control signal.
Furthermore, by adding an ultrasonic transmitter for transmitting ultrasonic transmission pulses by a control command received by the radio wave receiver, a reception device for receiving the ultrasonic transmission pulses transmitted from the ultrasonic transmitter, and a control portion for transmitting a control command from the radio wave transmitter based on an ultrasonic reception signal received by the reception device, a position of the natator in a water tank can be grasped and the operation of the natator in a water tank can be controlled based on the grasped position.
According to a third aspect of the present invention, a position measurement apparatus of a natator in a water tank is comprised of: a radio wave transmitter for transmitting a transmission command by radio waves to the natator in a water tank; a radio wave receiver which is provided to the natator in a water tank and receives radio waves transmitted from the radio wave transmitter; an ultrasonic transmitter for transmitting ultrasonic transmission pulses by a transmission command received by the radio wave receiver; at least three reception devices which are provided in a water tank and receive ultrasonic transmission pulses transmitted from the ultrasonic transmitter; a propagation time measurement portion for measuring ultrasonic wave propagation times from the ultrasonic transmitter to the respective reception devices based on a transmission monitor signal outputted from the radio wave transmitter and ultrasonic wave reception signals received by the respective reception devices; and a position calculation portion for calculating a three-dimensional position of the natator in a water tank from each propagation time of the ultrasonic waves measured by the propagation time measurement portion.
As a result, the propagation time of the ultrasonic waves from the natator in a water tank to each reception device can be measured by receiving the ultrasonic waves transmitted from the natator in a water tank by at least three reception devices, thereby calculating a three-dimensional position of the natator in a water tank based on each propagation time. At least three reception devices can suffice calculation of a three-dimensional position of the natator in a water tank. Therefore, if three or more reception devices are provided, the ultrasonic waves received by all the reception devices do not have to be considered, and three reception devices may be appropriately selected in accordance with a reception state so that only the ultrasonic waves received by the three selected reception devices can be considered.
Incidentally, a propagation time clock generation portion, a pulse counter, and a propagation time calculation portion may be provided instead of the propagation time measurement portion for measuring an ultrasonic propagation time in order to generate propagation time clock pulses whose number corresponds to an ultrasonic propagation time by the propagation time clock generation portion, count the propagation time clock pulses by the pulse counter, and calculate a propagation time of ultrasonic waves from the ultrasonic transmitter to each reception device based on a pulse count value.
In addition, the following method may be adopted in place of the above-described method by which a three-dimensional position of the natator in a water tank is sequentially calculated by the position calculation portion based on the propagation time of ultrasonic waves from the natator in a water tank to each reception device. That is, a three-dimensional position of the natator in a water tank is previously calculated based on the propagation time of the ultrasonic waves from the natator in a water tank to each reception device, and a data table of the ultrasonic propagation time and the three-dimensional position is created in advance. Then, a corresponding three-dimensional position is obtained from this data table based on the measured ultrasonic propagation time. By doing so, the three-dimensional position of the natator in a water tank can be also measured.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.